I took out a 5 year service plan (the Citroen "Freedrive" version) when I bought my DS4. I know that if the car works just fine needing nothing else then regular basic service, then I will end up paying more.
Financially I estimated the annual service cost to be around GBP 300.- to GBP 350. The service plan is approx. GBP 30/month (9000 km/year version).
But being my very first Citroen I was still a bit nervous about quality, and as the car is loaded with stuff that could be costly to repair (in Denmark everything with cars is expensive), I looked at the service plan as an insurance policy. For the 5 year period I have factory warranty, full service (all over Europe) and a fixed easy to budget monthly cost. All I have to cover myself is new tires. The day I want to sell the car, I also think that it will be a plus to be able to say that it has full service history under a service contract.
DS4 1.6 THP200 Sport in Babylon RED